[Mo^V₁₂O₃₀(μ₂-OH)₁₀H₂{Ni^II(H₂O)₃}₄], a Highly Symmetrical ε-Keggin Unit Capped with Four Ni^II Centers:  Synthesis and Magnetism

Abstract

The novel title compound {NiII 4MoV 12} demonstrates the concept of generating targeted spin topologies using reduced polyoxometalates: The four electrophilic nickel centersforming a tetrahedronare fixed by a nucleophilic highly reduced diamagnetic ε-Keggin cluster of T d symmetry generated in solution. This cluster not only has a structural role but actually participates in the transmission of the exchange interaction.

Observation of field-dependent magnetic parameters in the magnetic molecule{Ni4Mo12}

“…18 Because the structure of {Ni 4 Mo 12 } is almost perfectly tetrahedral one might anticipate that the magnetic energy levels are reasonably well described by an isotropic Heisenberg model with a single antiferromagnetic exchange parameter. 19 Such a Hamiltonian can be expressed in terms of the total spin: II ion in an octahedral ligand field is s = 1. For antiferromagnetic coupling (J < 0) the resulting low-temperature magnetization curve M(B) that follows from (1) displays four steps before reaching saturation.…”

Determination of spin Hamiltonian in the Ni4magnetic molecule

“…8. Our prompt-gamma neutron activation analysis showed that about 50% hydrogen was substituted by deuterium.…”

“…Distances between Ni 2+ ions within a cluster are 6.69, 6.70, 6.62, and 6.60Å, whereas the shortest distance between Ni 2+ ions that belong to different clusters is 7.15Å. Previous bulk property measurements using bulk susceptibility, high field magnetization, electron paramagnetic resonance, optical conductivity, and magneto-optical response [8][9][10] showed that the dominant interaction in the system is antiferromagnetic, which is due to the superexchange interaction through the Ni-O-Mo-ONi bonds. 9 The most interesting property of the Ni 4 nanaomagnet is an adiabatic change with non-equidistant steps observed in the magnetization measurements as a function of external magnetic field.…”

“…In the calculation of χ balk , the geometrical factor was taken to be g = 2.22. [8][9][10][11] The background due to isolated Ni 2+ ions was estimated by the Curie law and added to the calculated χ bulk . The existence of the biquadratic terms in H indicates a spin-lattice coupling in this system.…”

Gas-Phase Fragmentation Pathways of Mixed Addenda Keggin Anions: PMo12-nWnO403– (n = 0–12)

“…This also explains why, compared with the α and β isomers, the γ, δ, and ε structures are relatively unstable in the condensed phase. The γ isomers of select tungstates have previously been synthesized and isolated [41][42][43][44], and a few studies have reported the synthesis and characterization of ε-Keggin isomers with encapsulated ions [45][46][47].…”